Rechargeable battery systems lose capacity over time due to aging of the individual cells of a battery pack. As the cells age, and through many cycles of charging and discharging the battery pack, the number of amp-hours that the battery pack can store gradually decreases. At some point in the lifetime of a system, the system will no longer be able to provide its intended function. Temperature of operation of the cells, and the charging rate of the cells are among the factors that affect the aging of the cells and attendant loss of capacity. For example, a new electric vehicle may originally provide a 60 mile range, and, the owner may require the vehicle to travel 48 miles per charge. When the vehicle's battery system has degraded to the point of not being able to provide 48 miles of travel prior to having to be recharged, the vehicle becomes useless to the owner. The owner may have to decide between replacing the aged battery pack, at great expense, and selling the vehicle in order to purchase a new one.
It is within this context that the embodiments arise.